Variable speed portable electric hand tool



Jan. 2 0, 1970 v Kmmmonm'rls ETA!- 3,491,259

VARIABLE SPEED PORTABLE ELECTRIC HAND TOOL Filed Jan. 4, 1968 KESTUTIS DAMIJONAITIS DOMINIC J.COLAMUSSI ATTORNEYS INVENTORS United States Patent 3,491,259 VARIABLE SPEED PORTABLE ELECTRIC HAND TOOL Kestutis Damijonaitis, Newington, and Dominic J.

Colamussi, Kensington, Conn., assignors to The' Stanley Works, New Britain, Conn., a corporation of Connecticut Filed Jan. 4, 1968, Ser. No. 695,762 Int. Cl. H02k 11/00; H02p 7/36 US. Cl. 310-50 2 Claims ABSTRACT OF THE DISCLOSURE A rotatable speed control unit is mounted within the longitudinally extending handle of a sabre saw in tandem with the ON/OFF switch. The speed control unit includes a rotatable dial for varying the resistance of a rheostat, the dial having a slight peripheral portion projecting above the top surface of the handle in front of the ON/OFF switch button to facilitate rapid movement thereof during either right or left hand operation.

BRIEF SUMMARY OF THE INVENTION The present invention relates generally to portable, electric hand tools and is particularly concerned with a new and improved, variable speed control unit for such tools.

A principal object of the present invention is to provide a new and improved, variable speed, portable, electric hand tool having greater flexibility of operation coupled with ease and convenience of use during both right and left hand operation. Included in this object is the provision for a variable Speed control which enables the operator to preset and repeat predetermined speed settings.

Another object of the present invention is to provide a new and improved, portable, electric hand tool exhibiting continuous, full spectrum speed variability and including means for adjusting and predetermining the minimum and/or maximum speed of the tool thereby i enabling operation of the tool under conditions where variations in the mechanical components and tolerances a well as variations and tolerances of the electrical circuitry are overcome.

Still another object of the present invention is to provide a new and improved, portable hand tool of the type described which incorporates the desirable safety characteristics of providing for the advantageous presetting of the variable speed control at a minimum operating speed for the tool thereby requiring the use of the main ON/OFF switch by the operator for initiating or discontinuing the operation of the tool.

A further object of the present invention is to provide a sabre saw having the features mentioned hereinbefore and especially a speed control assembly located immediately adjacent the ON/OFF switch on the top of the handle so as to permit the smooth, easy thumb operation and control of both the switch and the variable speed setting. 9

Other objects will be in part obvious and in part pointed out more in detail hereinafter.

In accordance with the present invention these ben- 3,491,259 Patented Jan. 20, 1970 eficial characteristics can be incorporated into a portable hand tool by arranging in tandem within the tool handle both a rotatable speed control unit and an independently actuated ON/OFF switch both of which protrude above the handles top surface facing away from the housing of the tool. The speed control dial and the switch are located near the front of the tool along the handles longitudinal center line and are easily accessible to the operators thumb during normal operation of the tool thereby permitting easy thumb manipulation thereof during either right or left hand operation. The speed control dial includes a rotation barrier which can limit minimum and/or maximum operating speeds.

The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereafter set forth and the scope of the application which will be indicated in the appended claims.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a perspective view of a portable electric sabre saw incorporating the variable speed control unit of the present invention within the top handle thereof;

FIG. 2 is an enlarged sectional view taken along the line 2-2 of FIG. 1; and

FIG. 3 is an enlarged sectional view taken along the line 33 of FIG. 2.

DETAILED DESCRIPTION Referring now to the drawing in greater detail wherein like reference numerals indicate like parts throughout the several figures, the variable speed control unit of the present invention is shown as being encased within the handle of a portable, electric hand tool and will be described, for ease of illustration and clarity of understanding, in the environment of an electrically operated sabre saw. It will be appreciated, however, that the invention is not limited thereto but may be utilized in other portable electrically operated hand tools.

Referring to FIG. 1 of the drawing, the sabre saw generally designated 10 is provided with an elongated substantially rectangular housing 12 which encloses both the electric motor of the tool and the necessary mechanical components required to convert the rotating driving action of the motor into the reciprocating motion of the sabre saws plunger 14. The housing 12 supports an elongated, spadelike handle 16 which is conveniently positioned on top of the housing 12 to facilitate ready manipulation of the tool. The handle 16 is securely attached to the housing 12 at both the front and back thereof and extends longitudinally of the housing in spaced relationship thereto, thereby facilitating the secure grasping thereof by the operator. The handle 16 is longitudinally divided into right and left hand portions 20, 22, respectively, which are maintained in their fixed mating relationship by suitable fasteners 24. A power cord 26 by which current is supplied to the motor within the housing 12 passes through a rearwardly extending boss 28 in the handle and is suitably connected to the ON/ OFF switch of the tool. Adjacent its forward tapered end 32, the substantially fiat top surface 34 of the handle 16 is provided with a pair of generally rectangular tandemly arranged apertures 36, 38 of different size which extend longitudinally of the housing and respectively accommodate the exposed portion of the speed control unit 40 and the thumb operated button 42 of the ON/OFF switch, the latter being movable longitudinally between its respective ON and OFF positions. In FIG. 1, the button 42 is shown in its rearward or OFF position.

Referring now to FIGS. 2 and 3 of the drawing, the speed control unit 40, which is located forwardly of the ON/OFF switch adjacent the longitudinal center line of the handle, includes a cylindrical rheostat base member 48 which in the embodiment illustrated is mounted within the right portion 20 of the handle adjacent the front thereof with its axis disposed transversely of the handle 16. The base 48 is mounted in a fixed, firmly secured position and in this manner is prevented from rotating during the speed controlling operation of the tool. The rheostat is suitably wired intermediate the ON/ OFF switch and the electric motor in a conventional manner for regulating the current flow to the motor and thereby variably controlling the speed of the reciprocating plunger 14 of the sabre saw. The rheostat is so constructed and wired as to provide increased resistance to current flow upon rotation of the rheostats axial stem 50 in a counterclockwise direction as viewed in FIG. 3. Thus, by rotating the stern of the rheostat the speed of the sabre saw is varied correspondingly from its maximum number of strokes per minute to its minimum speed and subsequently to zero. To facilitate operatorcontrol over the speed of the saw, an externally manipulatable member is provided for rotating the rheostat stem 50. In the embodiment illustrated this takes the form of a speed control disk or dial 53 axially mounted in frictional engagement on the stem 50 of the rheostat'for rotation therewith. As best shown in FIG. 3, the dial 52 is of sufficient size so that a small portion of its serrated periphery 54 protrudes outwardly from the handle through the narrow, generally rectangular aperture 36 located at the tapered forward end 32 of the handles top surface 34. Thus, as the exposed portion of dial 52 moves forwardly in a clockwise direction as viewed in FIG. 3, it will correspondingly rotate stem 50 to reduce the operative resistance of the rheostat and effect an increase in the operating speed of the sabre saw. Due to the close proximity and tandem relationship of the dial 52 and switch button 42 in the'present invention the operator may, by a single uninterrupted forward movement of his thumb, turn on the tool and immediately adjustably increase the speed thereof. Conversely, a sweeping rearward movement of the operators thumb can effect a speed reduction and subsequent complete deactivation of the tool.

It is an added advantage of the present invention that the speed control unit 40 can be preset at a fixed maximum or minimum operating speed. This is particularly important since it provides the additional safety factor of requiring the operator to independently actuate the ON/OFF switch. In accordance with this embodiment of the present invention, the dial 52 is additionally provided with an arcuate noncontinuous channel 58 on the side thereof facing the rheostat base member 48. The channel 58 is medially spaced between the serrated peripheral edge 54 and a central axial bore 62 of the dial 52 which frictionally receives the stem 50 of the rheostat. The channel 58 extends coaxially about the bore 62 and circumscribes a suitable arc of less than 360, such as the arc of about 270 exemplified in FIG. 3. A fixed locating lug 64 carried by the rheostat base 48 and extending outwardly from the edge thereof toward the dial '52 is positioned within the channel 58 and, upon rotation of the dial, will abut the terminal walls 66, 68 of the channel to thereby limit the rotational movement of the rheostat stem.

Thus, it will be appreciated that the stem 50 may be rotated from its zero position to a point where minimum plunger speeds are in evidence for the purpose of selecting a predetermined minimum operating speed. Upon selecting this position the speed control dial 52 is frictionally mounted on the stem 50 with the locating lug 64 on the rheostat body positioned at the terminal wall 66 of the arcuate channel 58 thereby restricting movement of the stern in a direction of increased resistance or lower plunger speed. This position is illustrated in FIG. 3 of the draw ing and as can be seen therein limits further counterclockwise rotation of the rheostat stem. In this manner movement of the switch button 42 to an ON position will immediately result in operation of the sabre saw at its predetermined minimum operating speed and rotation of the dial 52 in a clockwise direction as viewed in FIG. 3 will rapidly increase the operation speed thereof.

As can be appreciated a similar limitation can be placed on the maximum speed setting of the tool by initially rotating the stem 50 from its minimum resistance position to any position of greater resistance for the purpose of selecting a predetermined maximum operatlng speed and the dial mounted thereon in such a manner that the lug 64 contacts terminal wall 68. The accuracy of the predetermined minimum and maximum settings is controlled by providing apertures 72 within the speed control dial at opposite ends of its channel. The apertures 72 extend through the dial 52 and enable the assembler to physically view the locating lug 64 as the dial is assembled on the rheostat stem, thus assuring the accurate positioning of the locating lug within the channel and thereby accurately controlling the assembly of the dial at the predetermined minimum and/or maximum speed desired for the hand tool.

The free end 74 of the rheostat stem 50 which projects outwardly of the dial bore 62 on the opposite side of the dial from the rheostat base is supportably positioned within the inwardly projecting boss 76 formed in the left hand portion 22 of the handle 16 so that when the handle halves 20, 22 are properly assembled, a rigid supporting structure is provided for the entire speed control unit 40.

As can be seen from the foregoing detailed description, the present invention provides a hand tool such as a sabre saw with a variable speed control unit which can be preset for maximum and/or minimum operating speeds and is conveniently located on the top surface of the handle of the saw immediately forward of and in tandem with the tools thumb operated ON/ OFF switch. In this manner the saw provides greater flexibility of operation coupled with ease and convenience of use during both right and left hand operation.

As will be apparent to persons skilled in the art, various modifications and adaptations of the structure above-described will become readily apparent without departure from the spirit and scope of the invention, the scope of which is defined in the appended calims.

We claim:

1. In a variable speed portable electric hand tool having an electric motor and an elongated housing enclosing said motor, an elongated handle securely attached to and extending longitudinally of the housing in spaced relationship thereto, said handle having a flat top surface facing away from the housing and extending along substantially the entire length of the housing, a rotatable speed control dial carried within the interior of the handle adjacent its longitudinal center line and having an axis of rotation extending transversely of the handle, said dial being fully enclosed by the handle with the exception of a minor peripheral portion protruding outwardly from said top surface for easy thumb manipulation during both right and left hand operation, a resistor mounted within the handle adjacent the dial for regulating the flow of current to the motor, said resistor including a rotatable stem mounting the dial for varying the resistance of the resistor by rotation of the dial, and a spaced independent ON/ OFF switch carried by the handle, said switch having a slidable control member protruding outwardly from said top surface of the handle immediately adjacent its longitudinal 5 6 center line for easy thumb manipulation in substantially 2,988,924 6/1961 Cooley. the same manner as the speed control dial. 3,085,169 4/ 1963 Abel 310-68 2. The tool of claim 1 wherein the dial and the inde- 3,221,192 11/1965 Franklin 310-68 pendent ON/ OFF switch are in tandem on the top sur- 3,280,351 10/1966 Wolter et a1. 310-68 face adjacent one end of the handle.

References Cited UNITED STATES PATENTS U.S. Cl. X.R.

2,581,806 1/1952 McShirley 318-130 310-68, 72

5 WARREN E. RAY, Primary Examiner 

